Conventionally, devices configured to apply an impact force of cavitation bubble collapse to cleaning, blending, beating, and the like have been widely known.
A device configured to inject high-pressure water into a liquid so as to generate cavitation around this high-pressure water has been disclosed as one of these devices (see Japanese Patent Laid-Open Publication No. Hei 11-19608, for example). However, this device applying the high-pressure water required high water pressure and had a problem that a cavitation effect tended to fluctuate due to viscosity, temperature, and the like of the liquid.
As a measure for solving such problems, a device configured to dispose a piezoelectric transducer, a magnetostrictive transducer or the like in contact with a container, and to generate cavitation by subjecting a liquid inside the container to ultrasonic vibration has been proposed (see Japanese Patent Laid-Open Publication No. 2002-25962, for example).
However, these publicly known conventional ultrasonic transducers cause ultrasonic vibration of the liquid inside through the container, and therefore had a problem that vibration was attenuated by the container and the cavitation effect was thereby reduced.
Here, it was also necessary to take an effect of a mechanical resonance frequency of the container into account beforehand, which caused a problem of complication of designing.